Bitumen/polymer compositions with improved stability and their application in carrying out surfacing operations

ABSTRACT

Bitumen/polymer compositions are provided containing a bitumen or a mixture of bitumens and, reckoned by weight of bitumen, 0.3% to 20% of at least one primary polymer selected among certain elastomers and plastomers and 0.01% to 12% of at least one olefinic polymer bearing epoxy or COOH groupings. The compositions are useful, directly or after dilution, to form bitumen/polymer binders for carrying out road surfacing, for coated materials or waterproof coatings.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to bitumen/polymer compositions having an improvedstability which is reflected, in particular, by a very good ability tobe stored while hot and by excellent mechanical properties. It furtherrelates to the application of the said compositions to the production ofsurfacings and in particular of road surfacings, of bituminous mixes oralternatively of watertight facings.

2. Background Art

It is known to use bituminous compositions as various surface coatingsand in particular as road surface coatings, provided that thesecompositions have a certain number of essential mechanical qualities.

These mechanical qualities are assessed, in practice, by determining, bystandardized tests, a series of mechanical characteristics, the mostwidely used of which are as follows:

softening temperature (abbreviated to RBT), expressed in 0° C. anddetermined by the ring-and-ball test defined by NF Standard T 66008,

brittleness point or Fraass point, expressed in 0° C. and determinedaccording to IP Standard 80/53,

penetrability, expressed in 1/10 of an mm and determined according to NFStandard T 66004,

tensile Theological characteristics, determined according to NF StandardT 46002 and comprising the quantities:

yield stress σ_(y) in bars,

elongation at yield stress ε_(y) in %,

breaking stress σ_(b) in bars,

elongation at break ε_(b) in %.

In general, conventional bitumens do not simultaneously exhibit all therequired qualities and it has been known for a long time that theaddition of varied polymers to these conventional bitumens makes itpossible to favourably modify the mechanical properties of the saidbitumens and to form bitumen/polymer compositions having improvedmechanical qualities with respect to those of the bitumens alone.

The polymers capable of being added to the bitumens can be elastomers,such as polyisobutylene, polyisoprene, polybutadiene, polychloroprene,butyl rubber, random ethylene/propylene (EP) copolymers, randomethylene/propylene/diene (EPDM) terpolymers, or polynorbornene, oralternatively plastomers, such as polypropylene, polyethylenes,ethylene/vinyl acetate copolymers, ethylene/methyl acrylate copolymersor ethylene/butyl acrylate copolymers.

Bitumen/polymer compositions based on a bitumen or mixture of bitumensand on one or more polymers of the abovementioned type have a limitedstability on storage. Phase separation takes place fairly quicklybetween the bituminous phase and the polymer phase with, as aconsequence, a deterioration in the physicomechanical properties of thesaid compositions after a relatively short storage time.

It has been found that the incorporation of olefinic polymers carryingepoxy or COOH functional groups in bitumen/polymer compositions composedof a bitumen or mixture of bitumens and of one or more polymers such asmentioned above significantly improved the stability of the saidcompositions on storage and, by the same token, ensured the maintenanceof, indeed even an improvement in, their physicomechanicalcharacteristics.

SUMMARY OF THE INVENTION

The subject of the invention is bitumen/polymer compositions withimproved stability comprising a bitumen or mixture of bitumens and, byweight of the bitumen or mixture of bitumens, 0.3% to 20% and moreparticularly 0.5% to 10% of at least one primary polymer chosen from thegroup formed by homopolymers of conjugated dienes, copolymers ofconjugated dienes with one another, polynorbornenes, polyisobutylenes,butyl rubber, homopolymers of C₂ to C₄ olefins, copolymers of ethyleneand of propylene, terpolymers of ethylene, of propylene and of a C₄ toC₁₂ diene or α-olefin, and copolymers of ethylene and of at least onemonomer A of formula ##STR1## where R₁ denotes H, CH₃ or C₂ H₅ and R₂represents a --COOR₅, --OR₅, --OOCR₆ or phenyl radical with R₅ denotinga C₁ to C₁₀ and preferably C₁ to C₆ alkyl and R₆ representing H or a C₁to C₃ alkyl, the said compositions being characterized in that theyadditionally contain, by weight of the bitumen or mixture of bitumens,0.01% to 12% and preferably 0.1% to 5% of an olefinic polymer containingepoxy or COOH functional groups chosen from copolymers containing, byweight, x % of units resulting from ethylene or propylene, y % of unitsresulting from one or more above-mentioned monomers A, z % of unitsresulting from at least one monomer B of formula ##STR2## and v % ofunits resulting from one or more monomers C other than the monomers Aand B, with R₁ denoting H, CH₃ or C₂ H₅, R₃ denoting H, COOH or COOR₅,R₄ representing a --COOH, ##STR3## radical, R₅ being a C₁ to C₁₀ andpreferably C₁ to C₆ alkyl radical and x, y, z and v representing numberssuch that 40≦x≦99.9, 0≦y≦50, 0.1≦z≦20 and 0≦v≦15 with x+y+z+v=100, withthe exception of the above bitumen/polymer compositions which contain,by weight of the bitumen or mixture of bitumens, either (i) 0.1% to 10%of olefinic copolymer containing epoxy groups and, simultaneously, asprimary polymers, 0.1% to 10% of a copolymer of ethylene and of amonomer having the formula ##STR4## R₁ and R₅ having the meaning givenabove, 0% to 10% of a thermoplastic elastomer D and 0% to 10% of an EVAcopolymer, or else (ii) 0.5% to 4% of olefinic copolymer containingepoxy groups and, simultaneously, as primary polymers used inconjunction, 2% to 6% of a thermoplastic elastomer D and 0.5% to 5% ofan EVA copolymer, the elastomer D being chosen from polybutenes,polybutadienes, polyisoprenes, ethylene/propylene copolymers,ethylene/butene copolymers and ethylene/diene copolymers.

Preferably, in the abovementioned copolymers, x, y, z and v are suchthat 50≦x≦99.5, 0≦y≦40, 0.5≦z≦15 and 0≦v≦10 with x+y+z+v=100.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The monomers A of formula ##STR5## which provide ##STR6## units in thecopolymer containing them, are chosen in particular from vinyl formate,vinyl acetate, vinyl propionate, vinyl butyrate, vinyl ethers CH₂═CH--O--R₅ where R₅ is a C₁ to C₁₀ and preferably C₁ to C₆ alkylradical, such as methyl, ethyl, propyl, butyl, pentyl or hexyl, or alkylacrylates and methacrylates of formula

    CH.sub.2 ═CH--COOR.sub.5

and ##STR7## respectively, where R₅ has the meaning given above.

The monomers B of formula ##STR8## which provide ##STR9## units in thefunctionalized olefinic copolymer, are chosen in particular from maleicacid and its anhydride, acrylic acid, methacrylic acid, alkyl hydrogenmaleates of formula HOOC--CH═CH--COOR₇ where R₇ is a C₁ to C₆ alkylradical, such as methyl, ethyl, propyl or butyl, glycidyl acrylates andmethacrylates of formula ##STR10## respectively, vinyl alcohol andglycidyl vinyl ether of formula ##STR11##

The monomers C, the presence of which in the olefinic copolymer isoptional, are monomers which can be polymerized by the radical routeother than the monomers A and B, such as, for example, CO, SO₂ andacrylonitrile.

In particular, the olefinic copolymers carrying epoxy or COOH functionalgroups are chosen from:

(a) random copolymers of ethylene and of a monomer B chosen from acrylicacid, methacrylic acid, maleic acid or its anhydride, glycidyl acrylateand glycidyl methacrylate which contain, by weight, 80% to 99.7% andpreferably 85% to 99.5% of ethylene;

(b) random terpolymers of ethylene, of a monomer A chosen from vinylacetate and alkyl acrylates or methacrylates containing a C₁ to C₆ alkylresidue, such as methyl, ethyl, propyl, butyl or hexyl, and of a monomerB chosen from acrylic acid, methacrylic acid, maleic acid or itsanhydride, glycidyl acrylate and glycidyl methacrylate which contain, byweight, 0.5% to 40% of units resulting from the monomer A and 0.5% to15% of units resulting from the monomer B, the remainder being formed ofunits resulting from ethylene; and

(c) copolymers resulting from the grafting of a monomer B chosen fromacrylic acid, methacrylic acid, maleic acid or its anhydride, glycidylacrylate and glycidyl methacrylate on a substrate composed of a polymerchosen from polyethylenes, in particular low density polyethylenes,polypropylenes and random copolymers of ethylene and of vinyl acetate orof ethylene and of alkyl acrylate or methacrylate containing a C₁ to C₆alkyl residue, such as methyl, ethyl, propyl, butyl or hexyl, whichcontain, by weight, 40% to 99.7% and preferably 50% to 99% of ethylene,the said grafted copolymers containing, by weight, 0.5% to 15% ofgrafted units resulting from the monomer B.

The olefinic copolymers containing epoxy or COOH functional groupschosen from:

(i) random terpolymers of ethylene, of alkyl acrylate or methacrylatecontaining a C₁ to C₆ alkyl residue, such as methyl, ethyl or butyl, andof maleic anhydride which contain, by weight, 0.5% to 40% of unitsresulting from alkyl acrylate or methacrylate and 0.5% to 15% of unitsresulting from maleic anhydride, the remainder being formed of unitsresulting from ethylene;

(ii) random terpolymers of ethylene, of alkyl acrylate or methacrylatecontaining a C₁ to C₆ alkyl residue, such as methyl, ethyl or butyl, andof glycidyl acrylate or methacrylate which contain, by weight, 0.5% to40% of units resulting from alkyl acrylate or methacrylate and 0.5% to15% of units resulting from glycidyl acrylate or methacrylate, theremainder being formed of units resulting from ethylene;

(iii) low density polyethylenes grafted with maleic anhydride andpolypropylenes grafted with maleic anhydride which contain, by weight,0.5% to 15% of grafted units resulting from maleic anhydride;

(iv) low density polyethylenes grafted with glycidyl acrylate ormethacrylate and polypropylenes grafted with glycidyl acrylate ormethacrylate which contain, by weight, 0.5% to 15% of grafted unitsresulting from the glycidyl derivative; are particularly preferred.

The olefinic copolymers carrying epoxy or COOH functional groups used toproduce the bitumen/polymer composition advantageously have molecularmasses such that the melt flow index of the said copolymers, determinedaccording to ASTM Standard D 1238 (test carried out at 190° C. under aload of 2.16 kg), has a value, expressed in grams per 10 minutes, ofbetween 0.3 and 3000 and preferably between 0.5 and 900.

The bitumen or mixture of bitumens which is used for the implementationthe process according to the invention is advantageously chosen from thevarious bitumens which have a kinematic viscosity at 100° C. of between0.5×10⁻⁴ m² /s and 3×10⁻² m² /s and preferably between 1×10⁻⁴ m² /s and2×10⁻² m² /s. These bitumens can be direct distillation or vacuumdistillation bitumens or else blown or semiblown bitumens, propane orpentane deasphalting residues, viscosity breaking residues, indeed evensome petroleum cuts or mixture of bitumens and of vacuum distillates oralternatively mixtures of at least two of the products which have justbeen listed. Besides a kinematic viscosity included within theabove-mentioned ranges, the bitumen or mixture of bitumens used in theprocess according to the invention advantageously exhibits apenetrability at 25° C., defined according to NF Standard T 66004, ofbetween 5 and 800 and preferably between 10 and 400.

The primary polymer can be in particular polybutadiene, polyisoprene,polychloroprene, butadiene/isoprene copolymers, polynorbornene,polyisobutylene, butyl rubber, high density polyethylene, low densitypolyethylene, polypropylene, polybutene, random ethylene/propylene (EP)copolymers, random ethylene/propylene/diene (EPDM) terpolymers,ethylene/vinyl acetate (EVA) copolymers, ethylene/C₁ to C₆ alkylacrylate copolymers, in particular ethylene/methyl acrylate copolymersand ethylene/butyl acrylate copolymers, and ethylene/C₁ to C₆ alkylmethacrylate copolymers, in particular ethylene/ethyl methacrylatecopolymers and ethylene/butyl methacrylate copolymers, ethylene/styrenecopolymers or ethylene/butene/styrene copolymers.

If appropriate, at least a portion of the primary polymer can becomposed of milled waste from the said polymer.

The bitumen/polymer composition is prepared by bringing the primarypolymer or polymers and the functionalized olefinic polymer or polymerscontaining epoxy or COOH groups into contact with the bitumen or mixtureof bitumens in proportions chosen within the ranges defined above, theoperation being carried out at temperatures of between 100° C. and 230°C., more particularly between 120° C. and 190° C., and with stirring,for a period of time of at least 10 minutes, generally of the order of afew tens of minutes to a few hours and, for example, from 10 minutes to8 hours and more particularly from 10 minutes to 5 hours, to form ahomogeneous mass constituting the bitumen/polymer composition. Theprimary polymer can be incorporated in the bitumen or mixture ofbitumens before or after the olefinic polymer containing epoxy or COOHgroups, it also being possible for a simultaneous incorporation to beenvisaged.

During its formation, the bitumen/polymer composition can also haveadded to it 1% to 40% and more particularly 2% to 30%, by weight of thebitumen, of a fluxing agent which can be composed, in particular, of ahydrocarbon oil exhibiting an atmospheric pressure distillation range,determined according to ASTM Standard D 86-67, of between 100° C. and600° C. and lying more especially between 150° C. and 400° C. Thishydrocarbon oil, which can in particular be a petroleum cut of aromaticnature, a petroleum cut of naphtheno-aromatic nature, a petroleum cut ofnaphtheno-paraffinic nature, a petroleum cut of paraffinic nature, acoal oil or alternatively an oil of plant origin, is sufficiently"heavy" to limit the evaporation at the time of its addition to thebitumen and, at the same time, sufficiently "light" to be removed asmuch as possible after the bitumen/polymer composition containing it hasbeen spread, so as to regain the same mechanical properties which thebitumen/polymer composition prepared without using any fluxing agentwould have exhibited after hot spreading. The fluxing agent can be addedto the reaction mixture, which is formed from the bitumen, from thesulphur-crosslinkable elastomer and from the sulphur-donor couplingagent, at any point in the formation of the said reaction mixture, theamount of fluxing agent being chosen, within the ranges defined above,in order to be compatible with the desired final use on the work site.

The mixture based on bitumen or mixture of bitumens, on primary polymeror polymers, on olefinic polymer(s) carrying epoxy or COOH groups andoptionally on fluxing agent, which gives rise to the bitumen/polymercomposition, can also contain one or more non-polymer additives capableof reacting with the epoxy or COOH groups of the functionalized olefinicpolymer. These reactive additives can in particular be primary orsecondary amines, especially polyamines, alcohols, especially polyols,acids, especially polyacids, or alternatively metal salts.

Reactive additives of the amine type are, for example, aromaticdiamines, such as 1,4-diaminobenzene, 2,4-diaminotoluene,diaminonaphthalene, bis(4-amino-phenyl) sulphone, bis(4-aminophenyl)ether or bis-(4-aminophenyl)methane, aliphatic or cycloaliphaticdiamines, such as those of formula H₂ N--R₁₃ --NH₂ where R₁₃ denotes aC₂ to C₁₂ alkylene or C₆ to C₁₂ cycloalkylene radical, for exampleethylenediamine, diaminopropane, diaminobutane, diaminohexane,diaminooctane, diaminodecane, diaminododecane, diaminocyclohexane,diaminocyclooctane or diaminocyclododecane, polyethylenepolyamines orpolypropylenepolyamines, such as diethylenetriamine,triethylenetetramine, tetraethylenepentamine or dipropylenetriamine, oralternatively fatty amines or polyamines, that is to say amines orpolyamines containing a C₁₂ to C₁₈ alkyl or alkenyl radical connected tothe nitrogen atom of an amine group.

Reactive additives of the alcohol type are, in particular, polyols, suchas diols or triols and especially diols of formula HO--R₁₄ --OH, whereR₁₄ denotes a hydrocarbon radical, especially a C₂ to C₁₈ alkylene, C₆to C₈ arylene and C₆ to C₈ cycloalkylene radical, and polyetherdiols offormula HO--[C_(q) H_(2q) O]_(r) H, where q is a number ranging from 2to 6 and especially equal to 2 or 3 and r is a number at least equal to2 and, for example, ranging from 2 to 20. Examples of such polyols areethylene glycol, propylene glycol, butylene glycol, diethylene glycol,triethylene glycol, tetraethylene glycol, hexanediol or octanediol.

Reactive additives of the acid type are, in particular, polyacids offormula HOOC--R₁₄ --COOH, where R₁₄ has the meaning given above.Examples of such polyacids are phthalic acid, terephthalic acid, malonicacid, succinic acid, adipic acid and glutaric acid.

Reactive additives of the metal salt type are, in particular, compounds,such as hydroxides, oxides, alkoxides, carboxylates, such as formatesand acetates, methoxides, ethoxides, nitrites, carbonates andbicarbonates, of metals from groups I, II, III and VIII of the PeriodicTable of the Elements, especially Na, K, Li, Mg, Ca, Cd, Zn, Ba, Al andFe.

The amount of the reactive additive or of the reactive additives whichare incorporated in the reaction mixture giving rise to thebitumen/polymer compositions can range from 0.01% to 10% and moreparticularly from 0.05% to 5% of the weight of bitumen present in thesaid reaction mixture.

In addition to the reactive additives and the fluxing agent, it is alsopossible to incorporate in the bitumen/polymer compositions, at any timein their formation, additives conventionally used in bitumen/polymercompositions, such as promoters of adhesion of the bitumen/polymercomposition to mineral surfaces or alternatively fillers, such as talc,carbon black or worn tyres reduced to fine powder.

When the bitumen/polymer composition contains a fluxing agent composedof a hydrocarbon oil as defined above, it is possible to produce thesaid bitumen/polymer composition by incorporating the olefinic polymercarrying epoxy or COOH groups and the primary polymer in the bitumen ormixture of bitumens in the form of a mother solution of these polymersin the hydrocarbon oil constituting the fluxing agent.

The mother solution is prepared by bringing ingredients composing it,namely hydrocarbon oil serving as solvent, olefinic polymer containingepoxy or COOH groups and/or primary polymer and, if appropriate,reactive additive, into contact at temperatures of between 10° C. and170° C. and more particularly between 40° C. and 120° C., and withstirring, for a sufficient period of time, for example between 10minutes and 2 hours, to obtain complete dissolution of the ingredientsin the hydrocarbon oil.

The respective concentrations of the various ingredients, in particularolefinic polymer containing epoxy or COOH groups, primary polymer and,if appropriate, reactive additive, in the mother solution can varyfairly widely, depending in particular on the nature of the hydrocarbonoil used to dissolve the said ingredients. Thus, the respective amountsof functionalized olefinic polymer and of primary polymer canadvantageously represent 1% to 20% and 5% to 30% by weight of thehydrocarbon oil.

In order to prepare the bitumen/polymer compositions by resorting to themother solution technique, the mother solution containing thefunctionalized olefinic polymer and the primary polymer and, ifappropriate, the reactive additives is mixed with the bitumen or mixtureof bitumens, the operation being carried out at temperatures of between100° C. and 230° C., more particularly between 120° C. and 190° C., andwith stirring, this being carried out, for example, by incorporating themother solution in the bitumen or mixture of bitumens kept stirring attemperatures between 100° C. and 230° C. and more particularly between120° C. and 190° C., and then the resulting mixture is kept stirring attemperatures of between 100° C. and 230° C., more particularly between120° C. and 190° C., for example at the temperatures used for carryingout the mixing of the mother solution with the bitumen, for a period oftime at least equal to 10 minutes and generally ranging from 10 minutesto 2 hours, to form a reaction product constituting the bitumen/polymercomposition.

The amount of mother solution mixed with the bitumen or mixture ofbitumens is chosen in order to provide the desired amounts, with respectto the bitumen, of olefinic polymer containing epoxy or COOH groups andof primary polymer, the said amounts being within the ranges definedabove.

The bitumen/polymer compositions with improved stability according tothe invention can be used as is or else diluted with variableproportions of a bitumen or mixture of bitumens or of a compositionaccording to the invention having different characteristics, toconstitute bitumen/polymer binders having a chosen content of polymerswhich can either be equal to (undiluted composition) or else lower than(diluted composition) the content of polymers in the correspondinginitial bitumen/polymer compositions. The dilution of thebitumen/polymer compositions according to the invention with the bitumenor mixture of bitumens or with a composition according to the inventionwith different characteristics can be carried out either directlyfollowing the preparation of the said compositions, when a virtuallyimmediate use of the resulting bitumen/polymer binders is required, orelse alternatively after a more or less prolonged period of storage ofthe bitumen/polymer compositions, when a delayed use of the resultingbitumen/polymer binders is envisaged. The bitumen or mixture of bitumensused for the dilution of a bitumen/polymer composition according to theinvention can be chosen from the bitumens defined above as beingsuitable for the preparation of the bitumen/polymer compositions.

The dilution of a bitumen/polymer composition by a bitumen or mixture ofbitumens or by a second composition according to the invention with alower content of polymers, in order to form a bitumen/polymer binderwith a chosen content of polymers lower than that of the bitumen/polymercomposition to be diluted, is generally carried out by bringing suitableproportions of the bitumen/polymer composition to be diluted and ofbitumen or mixture of bitumens or of second bitumen/polymer compositionaccording to the invention into contact, with stirring and attemperatures of between 100° C. and 230° C. and more particularlybetween 120° C. and 190° C.

The bitumen/polymer binders composed of the bitumen/polymer compositionsaccording to the invention or resulting from the dilution of the saidcompositions by a bitumen or mixture of bitumens or by anotherbitumen/polymer composition according to the invention, up to thedesired content of polymer (s) in the said binders, can be applied,directly or after conversion into aqueous emulsion, to the production ofroad surfacings of the surface coating type, to the production ofbituminous mixes which are put in place with heating or cold, or else tothe production of watertight facings.

The invention is illustrated by the following examples, given withoutimplied limitation.

In these examples, the amounts and percentages are expressed by weight,except when otherwise indicated.

In addition, the rheological and mechanical characteristics of thebitumens or of the bitumen/polymer compositions to which reference ismade in the said examples, namely penetrability and ring-and-ballsoftening point, are those defined above.

EXAMPLES 1 TO 6

Control bitumen/polymer compositions (Examples 1, 2 and 3) andbitumen/polymer compositions according to the invention (Examples 4, 5and 6) were prepared, in order to evaluate and compare thephysicomechanical characteristics thereof.

The preparations were carried out under the following conditions:

Example 1 (control)

965 parts of a bitumen having a penetrability, determined according tothe procedures of NF Standard T 66004, within the range 50/70 and 35parts of a random ethylene/vinyl acetate copolymer containing 18% ofvinyl acetate and having a melt flow index, determined according to ASTMStandard D 1238, having a value equal to 150 g per 10 minutes wereintroduced into a reactor maintained at 175° C. and with stirring. Thecontents of the reactor were subsequently maintained at 175° C., withstirring, for a period of time of 2.5 hours, to produce thebitumen/polymer composition.

Example 2 (control)

The preparation was carried out as described in Example 1, theethylene/vinyl acetate copolymer being replaced, however, by 20 parts ofa polynorbornene with a molecular mass greater than 2×10⁶ (Norsorexpolynorbornene from Elf Atochem), and 980 parts of bitumen being used.

Example 3 (control)

The preparation was carried out as described in Example 1, theethylene/vinyl acetate copolymer being replaced, however, by a lowdensity polyethylene having a melt flow index, determined as indicatedin Example 1, having a value equal to 1.2 g per 10 minutes.

Example 4 (according to the invention)

950 parts of the bitumen used in Example 1, as well as 35 parts of theethylene/vinyl acetate copolymer used in Example 1 and 15 parts of anethylene/methyl acrylate/glycidyl methacrylate terpolymer containing 24%of methyl acrylate and 8% of glycidyl methacrylate and having a meltflow index (ASTM Standard D 1238) having a value equal to 6 g per 10minutes were introduced into a reactor maintained at 175° C. and withstirring. The contents of the reactor were subsequently maintained at175° C., with stirring, for a period of time of 2.5 hours, to form thebitumen/polymer composition according to the invention.

Example 5 (according to the invention)

The preparation was carried out as described in Example 4, theethylene/vinyl acetate copolymer being replaced, however, by 20 parts ofthe polynorbornene employed in Example 2, and 972.5 parts of bitumen and7.5 parts of ethylene/methyl acrylate/glycidyl methacrylate terpolymerbeing used.

Example 6 (according to the invention)

The preparation was carried out as described in Example 4, theethylene/vinyl acetate copolymer being replaced, however, by the lowdensity polyethylene used in Example 3.

For each of the compositions obtained as indicated in Examples 1 to 6,the penetrability at 25° C. (Pen) and the ring-and-ball softeningtemperature (RBT) were determined.

In addition, a test of stability on storage at 180° C. for 3 days wascarried out on each of the bitumen/polymer compositions obtained. Thistest consists in filling an aluminium tube, "toothpaste tube" type, withthe composition to be studied and in maintaining the tube containing thecomposition at a temperature of 180° C. for the period of time chosenfor the storage, namely 3 days. At the end of the said period of time,the tube is cooled and is then cut into three parts having substantiallythe same length. The penetration at 25° C. and the softening temperatureof the composition are then determined in each of the top (upper third)and bottom (lower third) parts of the tube. The difference (Delta X)between the values of the characteristic X in the top part and thebottom part of the tube gives an indication of the stability of thebitumen/polymer composition. The composition becomes more stable as thedifference "Delta X" becomes smaller.

The results obtained are collated in the table below.

In this table, the abbreviations BT, EVA, PNB, LDPE and TPO have thefollowing meanings:

BT: unmodified bitumen with a penetrability within the range 50/70 usedin the various examples;

EVA: random ethylene/vinyl acetate copolymer used in Examples 1 and 4;

PNB: polynorbornene used in Examples 2 and 5;

LDPE: low density polyethylene used in Examples 3 and 6;

TPO: ethylene/methyl acrylate/glycidyl methacrylate terpolymer used inExamples 4, 5 and 6.

The contents of EVA, PNB, LDPE and TPO in the compositions are expressedas percentages by weight of the overall amounts of bitumen andpolymer(s).

                  TABLE                                                           ______________________________________                                        Examples     BT     1      2   3    4    5    6                               ______________________________________                                        EVA (%)             3.5             3.5                                         PNB (%)    2   2                                                              LDPE (%)    3.5   3.5                                                         TPO (%)     1.5 0.75 1.5                                                      Pen (1/10 mm) 68 48 45 50 54 50 53                                            RBT (° C.) 49 56 62 59 59 70 63                                      STORAGE AT 180° C. FOR 3 DAYS                                            Pen, Top (1/10 mm)                                                                           68     83   70  100  54   52   52                              Pen, Bottom (1/10 min) 68 42 30 30 53 50 50                                   Delta Pen (1/10 mm)  0 41 40 70  1  2  2                                      RBT, Top (° C.) 49 59 65 62 57 71 63                                   RBT, Bottom (° C.) 49 55 56 50 58 69 61                                Delta RBT (° C.)  0  4  9 12 -1  2  2                                ______________________________________                                    

In the light of the results presented in the table, it is apparent that:

the base bitumen is stable, as expected;

the bitumen/polymer compositions based on a bitumen and on a primarypolymer are all unstable on storage (Examples 1 to 3), thebitumen/polymer composition containing polyethylene (Example 3) beingthe most unstable;

the bitumen/polymer compositions according to the invention based on abitumen, on a primary polymer and on a functionalized olefinic polymer,in this instance functionalized by epoxy groups (Examples 4 to 6), arenotably more stable than the control bitumen/polymer compositions(Examples 1 to 3).

We claim:
 1. Bitumen/polymer compositions with improved stabilitycomprising a bitumen or mixture of bitumens and, by weight of thebitumen or mixture of bitumens, 0.3% to 20% of a primary polymerselected from the group consisting of polybutadiene, polyisoprene,polychloroprene, butadiene/isoprene copolymers, polynorbornene,polyisobutylene, butyl rubber, high density polyethylene, low densitypolyethylene, polypropylene, polybutene, random ethylene/propylenecopolymers, random ethylene/propylene/diene terpolymers, ethylene/vinylacetate copolymers, ethylene/styrene copolymers andethylene/butene/styrene copolymers, the said compositions additionallycontaining, by weight of the bitumen or mixture of bitumens, 0.01% to12% of at least one olefinic polymer containing epoxy functional groupsand a member selected from the group consisting of (a) random copolymersof ethylene and of a monomer B selected from the group consisting ofglycidyl acrylate and glycidyl methacrylate which contain, by weight,80% to 99.7% of ethylene, (b) random terpolymers of ethylene, of amonomer A selected from the group consisting of vinyl acetate, alkylacrylates containing a C₁ to C₆ alkyl residue and alkyl methacrylatescontaining a C₁ to C₆ alkyl residue and of a monomer B selected from thegroup consisting of glycidyl acrylate and glycidyl methacrylate whichcontain, by weight, 0.5% to 40% of units resulting from the monomer Aand 0.5% to 15% of units resulting from the monomer B, the remainderbeing formed from units resulting from ethylene and (c) copolymersresulting from the grafting of a monomer B selected from the groupconsisting of glycidyl acrylate and glycidyl methacrylate on a substratecomposed of a polymer selected from the group consisting ofpolyethylenes, polypropylenes, random copolymers of ethylene and ofvinyl acetate, random copolymers of ethylene and of alkyl acrylatecontaining a C₁ to C₆ alkyl residue and random copolymers of ethyleneand of alkyl methacrylate containing a C₁ to C₆ alkyl residue, whichcontain, by weight, 40% to 99.7% of ethylene, the said graftedcopolymers containing, by weight, 0.5% to 15% of grafted units resultingfrom the monomer B.
 2. Compositions according to claim 1 wherein theolefinic polymers containing epoxy groups are selected from the groupconsisting of:(i) random terpolymers of ethylene, of alkyl acrylate ormethacrylate containing a C₁ to C₆ alkyl residue and of glycidylacrylate or methacrylate which contain, by weight, 0.5% to 40% of unitsresulting from alkyl acrylate or methacrylate and 0.5% to 15% of unitsresulting from glycidyl acrylate or methacrylate, the remainder beingformed from units resulting from ethylene and (ii) low densitypolyethylenes grafted with glycidyl acrylate or methacrylate andpolypropylenes grafted with glycidyl acrylate or methacrylate whichcontain, by weight, 0.5% to 15% of grafted units resulting from theglycidyl acrylate or methacrylate.
 3. Bitumen/polymer compositions withimproved stability comprising a bitumen or mixture of bitumens and, byweight of the bitumen or mixture of bitumens, 0.3% to 20% of at leastone primary polymer selected from the group consisting of polybutadiene,polyisoprene, polychloroprene, butadiene/isoprene copolymers,polynorbornene, polyisobutylene, butyl rubber, high densitypolyethylene, low density polyethylene, polypropylene, polybutene,random ethylene/propylene copolymers, random ethylene/propylene/dieneterpolymers, ethylene/styrene copolymers and ethylene/butene/styrenecopolymers, the said compositions additionally containing, by weight ofthe bitumen or mixture of bitumens, 0.01% to 12% of at least oneolefinic polymer containing epoxy functional groups and a memberselected from the group consisting of (a) random copolymers of ethyleneand of a monomer B selected from the group consisting of glycidylacrylate and glycidyl methacrylate which contain, by weight, 80% to99.7% of ethylene, (b) random terpolymers of ethylene, of a monomer Aselected from the group consisting of vinyl acetate, alkyl acrylatescontaining a C₁ to C₆ alkyl residue and alkyl methacrylates containing aC₁ to C₆ alkyl residue and of a monomer B selected from the groupconsisting of glycidyl acrylate and glycidyl methacrylate which contain,by weight, 0.5% to 40% of units resulting from the monomer A and 0.5% to15% of units resulting from the monomer B, the remainder being formedfrom units resulting from ethylene and (c) copolymers resulting from thegrafting of a monomer B selected from the group consisting of glycidylacrylate and glycidyl methacrylate, on a polyethylene or polypropylenesubstrate, said grafted copolymers containing, by weight, 0.5% to 15% ofgrafted units resulting from the monomer B.
 4. Compositions according toclaim 1, wherein the content of primary polymer represents 0.5% to 10%of the weight of bitumen or mixture of bitumens.
 5. Compositionsaccording to claim 1, wherein the content of olefinic polymer containingepoxy or COOH functional groups represents 0.1% to 5% of the weight ofbitumen or mixture of bitumens.
 6. Compositions according to claim 1wherein, the olefinic polymers containing epoxy groups have a melt flowindex, determined according to ASTM Standard D 1238, having a value,expressed in grams per 10 minutes, of between 0.3 and
 3000. 7.Compositions according to claim 1, wherein the bitumen or mixture ofbitumens is chosen from bitumens having a kinematic viscosity at 100° C.of between 0.5×10⁻⁴ m² /s and 3×10⁻² m² /s.
 8. Compositions according toclaim 7, wherein the bitumen or mixture of bitumens exhibits apenetrability at 25° C., defined according to NF Standard T 66004, ofbetween 5 and
 800. 9. Compositions according to claim 1, wherein theyare obtained by bringing the primary polymer or polymers and theolefinic polymer or polymers containing epoxy groups into contact withthe bitumen or mixture of bitumens in the chosen proportions, theoperation being carried out at temperatures of between 100° C. and 230°C., and with stirring, for a period of time of at least 10 minutes, toform a homogeneous mass constituting the bitumen/polymer composition.10. Compositions according to claim 1, wherein they additionally contain1% to 40%, by weight of the bitumen or mixture of bitumens, of a fluxingagent.
 11. Compositions according to claim 10, wherein the fluxing agentis composed of a hydrocarbon oil exhibiting an atmospheric pressuredistillation range, determined according to ASTM Standard D 86-67, ofbetween 100° C. and 600° C.
 12. Compositions according to claim 11,wherein the hydrocarbon oil is selected from the group consisting ofpetroleum cuts of aromatic nature, petroleum cuts of naphtheno-aromaticnature, petroleum cuts of naphtheno-paraffinic nature, petroleum cuts ofparaffinic nature, coal oils and oils of plant origin.
 13. Compositionsaccording to claim 11 or 12, which are obtained by incorporating theolefinic polymer containing epoxy groups and the primary polymer in thebitumen or mixture of bitumens in the form of a mother solution of thesepolymers in the hydrocarbon oil constituting the fluxing agent. 14.Compositions according to claim 13, wherein the mother solutioncontains, by weight of the hydrocarbon oil, 1% to 20% of olefinicpolymer containing epoxy or COOH groups and 5% to 30% of primarypolymer.
 15. Compositions according to claim 13, which are obtained bymixing the mother solution with the bitumen or mixture of bitumens, theoperation being carried out at temperatures of between 100° C. and 230°C., and with stirring, and the resulting mixture then being keptstirring at temperatures of between 100° C. and 230° C., for a period oftime at least equal to 10 minutes, to form a reaction productconstituting the bitumen/polymer composition.
 16. Compositions accordingto claim 1, which contain one or more non-polymer additives capable ofreacting with the epoxy groups of the olefinic polymer carrying the saidgroups, the said reactive additives being primary or secondary amines,polyamines, alcohols, polyols, acids, polyacids, or alternativelycompounds of metals from groups I, II, III and VIII of the PeriodicTable of the Elements.
 17. Compositions according to claim 16, whereinthe amount of reactive additive or of reactive additives which theycontain represents 0.01% to 10% of the weight of the bitumen.
 18. Acoating composition comprised of a bitumen/polymer binder composed ofthe bitumen/polymer compositions of claim
 1. 19. A road surface coatingcomprised of the coating composition of claim
 18. 20. Watertight facingscomprised of the coating compositions of claim 18.